Diagnosing Carcinoid Tumors and Carcinoid Syndrome

Imaging Modalities Available for the Diagnosis of Carcinoid Tumors and Pancreatic Neuroendocrine Tumors

Once a detailed assessment of the patient's symptoms and laboratory results has been conducted and a diagnosis of neuroendocrine tumor (NET) is suspected, imaging will help confirm the diagnosis and assess the extent of disease.1 A variety of imaging methodologies is available for evaluating patients with NET, including structural/cross-sectional, functional, and endoscopic modalities1 (Table 7). Because primary tumors are difficult to localize in 20% to 50% of carcinoid tumors and in 10% to 60% of pancreatic NET (PNET), multiple imaging methods may be needed to detect NET.1,2

Table 7. Imaging Modalities by Location3-5
Location Imaging Modality
  • Multiphasic computed tomography scan
  • Magnetic resonance imaging3
  • Esophagogastroduodenoscopy3
  • Endoscopic ultrasound (EUS)3
  • Somatostatin receptor scintigraphy3
  • Positron emission tomography (PET)5
  • Abdominal/pelvic CT multiphasic scanor MRI3
  • PET5
Small bowel or colon
  • Abdominal/pelvic CT multiphasic scan or MRI
  • Somatostatin receptor scintigraphy
  • Colonoscopy3
  • EGD/EUS 3
  • Capsule endoscopy4
  • Enteroscopy4
  • PET5
  • Abdominal/pelvic CT multiphasic scan or MRI3
  • Somatostatin receptor scintigraphy 3
  • Colonoscopy3
  • Transrectal ultrasound 3
  • PET5

CT, computed tomography; EGD, Esophagogastroduodenoscopy EUS, endoscopic ultrasound; MRI, magnetic resonance imaging; PET, positron emission tomography.

Triple-phase computed tomography (CT) contrast-enhanced scans are useful for locating the primary tumor, mesenteric invasion, and thoracic lesions1 (Figure 8). Small NET are detected by maximizing the contrast between tumor and normal anatomical structures.1 Furthermore, NET are vascular tumors that enhance intensely with intravenous contrast during the early arterial phase of imaging and washout during the portal venous phase.6

Figure 8. Contrast-Enhanced Multiphasic Scan7

multiphasic-scan.jpg/Contrast-Enhanced Multiphasic Scan

Image reprinted with permission from Medscape.com. 2011. http://www.medscape.com/viewarticle/410855.

Magnetic resonance imaging (MRI) allows localization of carcinoid tumors and/or metastases1 ; detection of NET with CT or MRI is 22% to 45%.2

MRI is preferred over CT in patients who have an allergy to contrast dye or renal insufficiency.8 Gadolinium-enhanced MRI can also assist in identifying liver lesions.1

Endoscopic ultrasound (EUS, Figure 9), small-bowel series and abdominal sonography are recommended methods for identifying primary NET and metastases.1 Carcinoid tumors of the stomach can be imaged using EUS or endoscopy.4 EUS can detect whether larger gastric carcinoid tumors are invasive lesions.1 EUS can also detect 45% to 60% of duodenal lesions, and 90% to 100% of pancreatic lesions (Figure 10).2 EUS with fine-needle aspiration can also differentiate a nonfunctional PNET from an adenocarcinoma.1 Capsule endoscopy is often used to detect carcinoid tumors in the jejunum and ileum that are difficult to detect with other imaging modalities.9 In the hindgut, EUS is ideal for evaluating localized rectal carcinoid tumors.10 (Figure 11). Ultrasonography can detect 13% to 27% of NET.2

Figure 9. Primary Carcinoid Tumors by Endoscopy and EUS

primary-carcinoid-tumors.jpg/Primary Carcinoid Tumors by EUS

Images provided by Jeffrey H. Lee, MD, FACG, FASGE. Department of Gastroenterology, Hepat,& Nutr, Division of Internal Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX

Figure 10. Endoscopic Ultrasound11

endoscopic-ultrasound.jpg/Endoscopic Ultrasound

Re-printed with permission from: McLean A. Cancer Imaging. 2004: 4; 84-91.

Figure 11. Capsule Endoscopy12

metastatic-gastrointestinal-carcinoid-tumor /Metastatic Gastrointestinal Carcinoid Tumor Capsule Endoscopy

Reprinted from Liang PS, Shaffer K. Radiol Case Rep. 2007;2:90, with permission from Creative Commons Attribution-NonCommercial-NoDerivs 2.5 License.

Somatostatin receptor scintigraphy (SRS) is the primary imaging modality for localization of primary and metastatic NET2 (Figure 12). SRS is the most sensitive modality for identification of hepatic metastases.2 SRS is also useful in confirming a diagnosis and evaluating tumor distribution and burden.1

Positron emission tomography (PET) with fluorodeoxyglucose (FDG) detects poorly differentiated or undifferentiated NET such as bronchus and thymus small-cell-like lesions, and highly aggressive NET.1,2,8 Single photon emission computed tomography (SPECT) and PET-CT permit the correlation of NET location with clinical function.2 11 C-5-hydroxytryptophan PET may have better tumor visualization than scintigraphy.8 PET imaging with radioisotope 131I-metaiodobenzylguanidine (I-MIBG) detects carcinoid tumors in the jejunum, ileum, cecum, and appendix (midgut).8 Small-bowel series and PET also are used for midgut.1

Figure 12. Somatostatin Receptor Scintography12

gastrointestinal-carcinoid-tumor.jpg/Metastatic Gastrointestinal Carcinoid Tumor

Reprinted from Liang PS, Shaffer K. Radiol Case Rep. 2007;2:90, with permission from Creative Commons Attribution-NonCommercial-NoDerivs 2.5 License.

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  1. Vinik AI, Woltering EA, Warner RR et al. NANETS consensus guidelines for the diagnosis of neuroendocrine tumor. Pancreas. 2010;39:713-734.
  2. Oberg K, Castellano D. Current knowledge on diagnosis and staging of neuroendocrine tumors. Cancer Metastasis Rev. 2011;30(suppl 1):3-7.
  3. National Comprehensive Cancer Center. NCCN clinical practice guidelines in oncology: neuroendocrine tumors. 2010. https://www.nccn.org/professionals/physician_gls/PDF/neuroendocrine.pdf. Accessed June 27, 2016.
  4. Modlin IM, Kidd M, Latich I, Zikusoka MN, Shapiro MD. Current status of gastrointestinal carcinoids. Gastroenterology. 2005;128:1717-1751.
  5. Eriksson B, Bergström M, Orlefors H, Sundin A, Oberg K, Långström B. Use of PET in neuroendocrine tumors. In vivo applications and in vitro studies. Q J Nucl Med. 2000;44:68-76.
  6. Kulke MH, Anthony LB, Bushnell DL et al. NANETS treatment guidelines: well-differentiated neuroendocrine tumors of the stomach and pancreas. Pancreas. 2010;39:735-752.
  7. Paulson EK. Evaluation of the liver for metastatic disease. Semin Liver Dis. 2001;21:225-236. http://www.medscape.com/viewarticle/410855_2.
  8. Boudreaux JP, Klimstra DS, Hassan MM et al. The NANETS consensus guideline for the diagnosis and management of neuroendocrine tumors: well-differentiated neuroendocrine tumors of the jejunum, ileum, appendix, and cecum. Pancreas. 2010;39:753-766.
  9. Scherübl H, Jensen RT, Cadiot G, Stölzel U, Klöppel G. Neuroendocrine tumors of the small bowels are on the rise: early aspects and management. World J Gastrointest Endosc. 2010;2:325-334.
  10. Anthony LB, Strosberg JR, Klimstra DS et al. The NANETS consensus guidelines for the diagnosis and management of gastrointestinal neuroendocrine tumors (nets): well-differentiated NET of the distal colon and rectum. Pancreas. 2010;39:767-774.
  11. McLean A. Endoscopic ultrasound in the detection of pancreatic islet cell tumours. Cancer Imaging. 2004;4:84-91.
  12. Liang PS Shaffer K. Metastatic gastrointestinal carcinoid tumor with unknown primary site. Radiol Case Rep. 2007;2:90.